Illuminating Unit and Imaging Apparatus

ABSTRACT

There is provided a small sized imaging apparatus which can measure with high accuracy a color distribution of a surface of an object, in which a light intensity distribution on a predetermined surface in a direction substantially perpendicular to an optical axis is uniform, and a change in an amount of light in a direction along the optical axis is reduced, and an illuminating unit which used in this imaging apparatus. (The imaging apparatus) Includes a light source section ( 210 ) which supplies illuminating light, a diffusing section ( 211 ) which diffuses by reflecting the illuminating light from the light source section ( 210 ), and aperture sections ( 212   a  and  212   b ) which allow to emerge diffused illuminating light, and the aperture sections ( 212   a  and  212   b ) has an aperture diameter D which allows the diffused illuminating light to emerge as a substantially parallel light.

TECHNICAL FIELD

The present invention relates to an illuminating unit, and an imagingapparatus which includes the illuminating unit.

BACKGROUND ART

For example, paint on a surface of a passenger automobile, a gloss and acolor of a tooth of a human being has been hitherto measured over apredetermined range. Moreover, based on measurement results, anunevenness of the gloss, an unevenness of the color of the tooth, and anunevenness of the paint of an object is calculated. Particularly, in afield of dental treatment, many a times, a dentist makes a judgment ofthe color of tooth, a color tone, and the gloss. For this, apredetermined range of tooth is illuminated by an illuminating unit. Alight emitting diode (hereinafter called as “LED”) can be used as alight source of the illuminating unit. A structure of a color measuringapparatus in which the LED is used is proposed in Japanese Patent No.3218601.

The unevenness of the color, the color tone, and the gloss is calculatedbased on a light scattered from the surface. Optical characteristics ofthe surface of the object, for example “a distribution of the color, thecolor tone, and the gloss” will be hereinafter called generically as“color distribution”. Therefore, for measuring accurately the colordistribution of the surface of the object, it is necessary to illuminateby light of a uniform intensity distribution.

However, normally, spatial light distribution characteristics of thelight from the LED are not uniform. Therefore, the intensitydistribution of the light from the LED has non-uniformity to certainextent. In the structure of the Japanese Patent No. 3218601 mentionedabove, light of three primary colors from the LED is irradiated directlyon a surface to be irradiated of the object. Therefore, an unevenness ofthe light intensity distribution is developed on the surface to beirradiated of the object. As a result of this, the color distribution ofthe surface of the object cannot be measured accurately.

Moreover, for example, in many cases the dentist measures the colordistribution of a tooth by holding an imaging apparatus in a hand. Atthis time, the imaging apparatus is not fixed mechanically. As a resultof this, a gap between the imaging apparatus and the tooth which is anobject, in other words an imaging distance along a direction of anoptical axis, is changed sometimes during the measurement of the colordistribution. Moreover, in the structure in Japanese Patent No. 3218601,when a gap between a color measuring apparatus and the object ischanged, the unevenness in the light intensity distribution of theilluminated light is increased. Thus, the structure in the JapanesePatent No. 3218601 is a problem due to an occurrence of the uneven lightintensity distribution caused by a change in the imaging distance alongthe direction of the optical axis. This problem becomes even moreremarkable when the object is three-dimensional.

Furthermore, when the illuminating unit illuminates the surface of theobject, a scattered light and a specularly (regularly) reflected lightare generated. The unevenness of the paint of the object, or theunevenness of the color, the color tone, and the gloss are calculatedbased on the scattered light from the surface. Therefore, at the time ofmeasuring the color distribution of the surface of the object, itbecomes necessary to capture an image of the scattered light from thesurface. Whereas, the specularly reflected light from the surface of theobject has the light intensity substantially higher as compared to thescattered light. As a result of this, when the specularly reflectedlight (which is reflected) from the surface is incident on an imagingoptical system, the color distribution of the surface cannot be measuredaccurately.

In the structure in the Japanese Patent No. 3218601, an angle between anoptical axis of the LED which is an illuminating optical system, and acentral axis of a photodiode of an imaging element is small. Therefore,out of the light irradiated from the LED, the light which is specularlyreflected at the surface of the object is incident on the photodiode. Asa result of this, the unevenness of the color of the surface of theobject cannot be measured accurately, which is a problem. Particularly,when the object has a gloss, the light intensity of the specularlyreflected light becomes higher. Therefore, in the structure of theconventional technology, in a case of the object having a gloss, thisproblem becomes even more remarkable.

For reducing the specularly reflected light from the surface of theobject, widening an angle between the optical axis of the illuminatingoptical system, and an optical axis of an imaging optical system can betaken into consideration. Here, sometimes the object is athree-dimensional structure. In this case, when the angle between theoptical axis of the illuminating optical system and the optical axis ofthe imaging optical system is wide, a shadow portion occurs in theobject. The shadow portion of the object cannot acquire information fromthe surface.

Thus, it is necessary that the shadow is not developed in the object,while reducing the specularly reflected light. Therefore, disposing theilluminating optical system in two directions facing each other, withthe imaging optical system as a center can be taken into consideration.The illuminating light from the illuminating optical system is let to beincident obliquely on the object. Accordingly, it is possible to reducethe specularly reflected light, and to avoid the shadow from developingon the object. However, it is necessary to dispose at least twoilluminating optical systems around the imaging optical system. As aresult of this, there is a problem that a size of the imaging apparatusbecomes big. Particularly, in the field of dental treatment where atooth is let to be the object, a reduction in the size of the imagingapparatus is desired strongly.

The present invention is made in view of the abovementioned problems,and it is an object of the present invention to provide an imagingapparatus of a small size which is capable of measuring with highaccuracy a color distribution of a surface of an object, in which alight intensity distribution on a predetermined surface in a directionsubstantially perpendicular to an optical axis is uniform, and a changein an amount of light in a direction along the optical axis is reduced,and an illuminating unit which is used in this imaging apparatus.

Moreover, another object of the present invention is to provide animaging apparatus of a small size which is capable of measuring withhigh accuracy a color distribution of a surface of an object by a brightdiffused light, and an illuminating unit which is used in this imagingapparatus.

DISCLOSURE OF THE INVENTION

For solving the abovementioned issues, and attaining the object,according to a first invention, it is possible to provide anilluminating unit which includes a light source section which suppliesan illuminating light, a diffusing section which diffuses by reflectingthe illuminating light from the light source section, and an aperturesection which allows the diffused illuminating light to emerge, and theaperture section has a diameter which allows the diffused illuminatinglight to emerge as a substantially parallel light.

Moreover, according to a second invention, it is possible to provide anilluminating unit which includes a light source section which suppliesan illuminating light, a diffusing section which diffuses by reflectingthe illuminating light from the light source section, and an aperturesection which allows the diffused illuminating light to emerge, and thelight source section is provided at a position at which the illuminatinglight supplied by the light source section is emerged from the aperturesection upon being reflected at least once in the diffusing section.

Furthermore, according to a third invention, it is possible to providean imaging apparatus which includes the illuminating unit, and animaging optical system which forms an image of a reflected light from anirradiated surface which is illuminated by the illuminating unit, and acolor distribution of the irradiated surface is calculated based on thereflected light acquired by the imaging optical system.

There is shown an effect that the imaging apparatus according to thepresent invention can measure with high accuracy a color distribution ofa surface of an object, in which a light intensity distribution on apredetermined surface in a direction substantially perpendicular to anoptical axis is uniform, and a change in amount of light in a directionalong the optical axis is reduced. Moreover, there is shown an effectthat the imaging apparatus according to the present invention is smallsized, and can measure with accuracy a color distribution of a surfaceof an object by a bright diffused light.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a formation of a system which uses animaging apparatus according to a first embodiment;

FIG. 2 is a block diagram of the system which uses the imaging apparatusaccording to the first embodiment;

FIG. 3 is a diagram showing briefly an optical system portion of thefirst embodiment;

FIG. 4 is a perspective structure diagram of an illuminating unit of thefirst embodiment;

FIG. 5 is a top surface view of the illuminating unit of the firstembodiment;

FIG. 6 is a cross-sectional structure diagram of the illuminating unitof the first embodiment;

FIG. 7A is a diagram showing a relation between a size of an aperturesection and an emerged light;

FIG. 7B is another diagram showing the relation between the size of theaperture section and the emerged light;

FIG. 8 is a diagram showing a spectral distribution of an LED;

FIG. 9 is a diagram showing a relation between a position of theaperture section and an intensity distribution at an optical axis;

FIG. 10A is a diagram showing a cross-sectional structure of a diffusingsection of the first embodiment;

FIG. 10B is a diagram showing a cross-sectional structure of anotherdiffusing section of the first embodiment;

FIG. 10C is a diagram showing a cross-sectional structure of stillanother diffusing section of the first embodiment;

FIG. 11 is a top surface view of an illuminating unit of a secondembodiment;

FIG. 12 is a cross-sectional structure diagram of the illuminating unitof the second embodiment;

FIG. 13 is a cross-sectional structure diagram of an illuminating unitof a third embodiment;

FIG. 14A is a diagram showing a structure of an LED of the thirdembodiment;

FIG. 14B is a diagram showing another structure of the LED of the thirdembodiment; and

FIG. 14C is a diagram showing still another structure of the LED of thethird embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of an illuminating unit and an imaging apparatus accordingto the present invention will be described below in detail withreference to the accompanying diagrams. However, the present inventionis not restricted to the embodiments described below.

FIRST EMBODIMENT

FIG. 1 shows a formation for use of an imaging apparatus 100. Theimaging apparatus 100 is an apparatus used for application of measuringaccurately a gloss and a color of a tooth of a human being as an objectOBJ, for example.

As shown in FIG. 1, a system which uses the imaging apparatus 100includes the imaging apparatus 100, a cradle 101, and a computer 102.The imaging apparatus 100 performs imaging of the object OBJ such as atooth. After the imaging, the imaging apparatus 100 is mounted on thecradle 102. Accordingly, the cradle 101 is electrically connected to theimaging apparatus 100. By electrically connecting the cradle 101 to theimaging apparatus 100, the cradle 102 receives imaging data from theimaging apparatus 100. At the same time, the cradle 101 charges theimaging apparatus 100.

The computer 102 is connected to the cradle 101. The computer 102receives the imaging data via the cradle 101. Next, the computer 102performs a predetermined analysis process based on the imaging data.

By using such a system, for example, a dentist performs imaging of asurface of a human tooth and performs the analysis process. Here, adental treatment which recuperates the damaged tooth is considered. Atthis time, it is desirable that the tooth before the recuperation andthe tooth after the recuperation, such as an artificial tooth, have thesubstantially same color distribution. So far, the artificial tooth hasbeen manufactured based on a subjective judgment by the dentist. At thetime of making the judgment, sometimes an artificial tooth in which acolor distribution with an adjacent tooth is not matched due to adifference in an illuminating environment when an original tooth isobserved and when the artificial tooth is manufactured, and a differenceof the observing person, is manufactured, and the artificial tooth is tobe remade.

Whereas, the dentist who uses this system, measures the colordistribution of the original tooth before recuperation, or measures thecolor distribution of the tooth which is adjacent to the tooth to berecuperated. Further, an artificial tooth having the color distributionmatching with the color distribution acquired by the analysis process ismanufactured. Thus, according to this system, it is possible to comparethe color distribution of the tooth after the recuperation and the colordistribution of the tooth before the recuperation based on objectiveimage data, without depending on the subjective judgment of the dentist.As a result, by using this system, it is possible to prevent themismatching of the color of the artificial tooth due to the differenceof a person and the difference of the illuminating environment, and toreduce a possibility of remaking the artificial tooth.

Moreover, in recent years, in dentistry, a so-called whitening processwhich is a treatment of processing a surface of a tooth to a naturalwhite color has been performed. Once a patient is used to the color ofthe tooth after the treatment, the patient feels that the color has beenthe original color of the tooth, and is sometimes skeptical about aneffect of the treatment. At the time of performing the whiteningprocess, the dentist by using this system can check objectively thewhiteness of the tooth after the process, and some times as a numericalvalue. Consequently, the patient who has received the whiteningtreatment can realize the effect as an objective numerical value, and itis possible to reduce an unwanted doubt and dissatisfaction due to avague memory and a wrong impression.

Next, a system which uses the imaging apparatus 100 will be described byreferring to FIG. 2. FIG. 2 is a block diagram showing a schematicstructure of this system.

A hood 106 for the object OBJ is installed in an extended form on a mainbody 105 of the imaging apparatus 100. The object OBJ is, for example, atooth in the dental treatment. Moreover, a power supply switch 107, ashutter button 108, a contact point 109, an LCD unit 110, and a focusring 111 are formed on an outer surface of the main body 105. The powersupply switch 107 puts ON or OFF a power supply of the imaging apparatus100. The shutter button 108 makes an indication input of an imagingoperation. The contact point 109 electrically connects the cradle 101and the imaging apparatus 100. The LCD unit 110 performs a display of animage which is captured, and a display of various types of informationrelated to the imaging apparatus 100. Moreover, by an operation of thefocus ring 111, it is possible to adjust manually a focal position of animaging optical system 121 which will be described later.

An illuminating unit 200, the imaging optical system 121, and a CCD 113are disposed inside the main body 105. The illuminating unit 200irradiates illuminating light which illuminates the object OBJ. Adetailed structure of the illuminating unit 200 will be described later.The imaging optical system 121 forms on a predetermined surface an imageof a scattered light from a surface of the object OBJ which isilluminated. The imaging optical system 121 has a lens structure whichcan form an image of the object OBJ at the most close distance. The CCD113 which is an imaging device performs imaging of the object OBJ bylight which is transmitted through the imaging optical system 121. Here,the predetermined surface or a surrounding of the predetermined surfaceand a light receiving surface of the CCD 113 are disposed to coincide.The CCD 113 converts an image of the object OBJ which is formed byimaging optical system 121, to an electrical image signal.

The hood 106 shields unnecessary external light. Accordingly, the hood106 can guide efficiently only the scattered light which is reflectedfrom the surface of the object OBJ to the imaging optical system 121.Moreover, it is possible to adjust a position of the imaging opticalsystem by operating manually the focus ring 111 by an operator such as adentist. An imaging position of the object OBJ by the imaging opticalsystem 121, and the light receiving surface of the CCD 113 are allowedto coincide by the operation of the focus ring 111. Instead of using thefocus ring 111, a structure which can adjust a focal point automaticallyby a heretofore known auto-focusing mechanism may be used.

Furthermore, an electric circuit board 112 is provided inside the mainbody 105. A signal processing circuit 114, an LED controller 115, acontrolling circuit 118, a memory 116, and a power supply circuit 117are installed on the electric circuit board 112.

The signal processing circuit 114 performs various signal-processing ofan image signal which is output from the CCD 113. The LED controller 115controls a light emission state of an LED included in the illuminatingunit 200. The memory 116 performs storing of image data processed by thesignal processing circuit 114, and storing of data and processingcomputer program executed by a control circuit 118 which will bedescribed later. A battery 119 accumulates a power supply which is to besupplied from the cradle 101 to the imaging apparatus 100 via thecontact point 109. The power supply circuit 117 supplies the powersupply which is supplied from the battery 119 to each circuit inside theimaging apparatus 100. Moreover, the control circuit 118 is connected inboth directions to the illuminating unit 100, the signal processingcircuit 114, the LED controller 115, the memory 116, and the powersupply circuit 117, via a bus etc. The control circuit 118 performs acomprehensive control of the entire imaging apparatus 100.

As shown in FIG. 1, a grip portion 105 b for the operator to hold in ahand is provided on the imaging apparatus 100. The shutter button 108 isdisposed at a position operable by a forefinger etc. of the hand holdingthe grip portion 105 b. Moreover, the power supply switch 107 isdisposed at a position on a side opposite to the shutter button 108,such as a position operable by a thumb etc. of the hand holding the gripportion 105 b for example. Furthermore, the contact point 109 isprovided on the grip portion 105 b. The battery 119 is disposed insidethe grip portion 105 b. Moreover, the LCD unit 110 is disposed at aneasily observable position on a rear side of the main body 105 of theimaging apparatus. 100.

Next, the cradle 101 will be described. A contact point 139, an ACadaptor 135, an A/D converting circuit 134, and a power supply circuit136 are disposed in the cradle 101. The contact point 139 iselectrically connected to the contact point 109 of the imaging apparatus100. The AC adaptor 135 converts a predetermined AC voltage which issupplied from an AC power supply to an appropriate DC voltage. The A/Dconverting circuit 135 performs a conversion to digital data when theimage data transmitted from the imaging apparatus 100 is analog data.The power supply circuit 136 supplies the power supply supplied from theAC adaptor 135, to each circuit therein.

An SRAM 133, an FPGA (Field Programmable Gate Array) 132, an interface(I/F) 137 of a USB 2, and a CPU 131 are further disposed in the cradle101. The SRAM 133 performs storing of image data and storing of data andprocessing computer program executed by the CPU 131 which will bedescribed later. The FPGA 132 performs a compression process of theimage data. The I/F 137 of the USB 2 performs communication with thecomputer 102 by the USB 2 for example. Moreover, the CPU 131 isconnected in both directions to the FPGA 132, the SRAM 133, the A/Dconverting circuit 134, the power supply circuit 136, and the I/F 137,via a bus etc. The CPU 131 performs a comprehensive control of theentire cradle 102 and a control of communication with the imagingapparatus 100, and a control of communication with the computer 102.

Moreover, the computer 102 is connected to the cradle 101 via the USB 2for example. A color analyzing software 141 is installed in the computer102. The color analyzing software 141 performs an analysis process ofthe image data received from the imaging apparatus 100. Accordingly, itis possible to calculate a color distribution of the object OBJ.Moreover, a color database 142 is stored in a memory of the computer 102which is not shown in the diagram. The color analyzing software 141refers to the color database 142 at the time of performing the analysisprocess of the image data.

FIG. 3 shows briefly a structure mainly of an optical system, in thesystem which uses the imaging apparatus according to the firstembodiment. The illuminating unit 200 illuminates the object OBJ.Details of the illuminating unit 200 will be described by using FIG. 4,FIG. 5, and FIG. 6. Scattered light from the object OBJ passes through acentral portion of the illuminating unit 200. The scattered light whichis passed is incident on the imaging optical system 121. Light emergedfrom the imaging optical system 121 is imaged at the CCD 113. Moreover,the illuminating unit 200 is provided in an optical path between the CCD113 which is an imaging optical system, and an irradiated surface of theobject OBJ.

As it will be described later, the illuminating unit 200 sequentiallyilluminates the object OBJ by light in a predetermined wavelength range.The scattered light reflected from the object OBJ which is illuminatedby the light in the predetermined wavelength range is incident on theimaging optical system 121. Next, light from the imaging optical system121 is received at the CCD 113. Further, as it has been described above,the computer 102 performs an analysis process of the color distributionof the surface of the object OBJ based on the image data from the CCD113. The color distribution of the tooth which is an analysis result isdisplayed on a display 102 d.

(Structure of Illuminating Unit)

FIG. 4 shows a perspective structure of the illuminating unit 200 asseen from a side of the object OBJ. The illuminating unit 200 has alight source section 210, a diffusing section 211, a first aperturesection 212 a, and a second aperture section 212 b. The light sourcesection 210 is made of a plurality of LEDs which supply the illuminatinglight. The diffusing section 211 diffuses by reflecting the illuminatedlight from the light source section 210. The first aperture section 212a and 212 b allows the diffused illuminating light to emerge. Thediffusing section 211 is structured to be square cylindrical shaped.Moreover, a center of a hollow portion of the diffusing section 211 andan optical axis AX of an imaging optical system which is not shown inthe diagram are allowed to coincide substantially.

Next, a further detailed structure of the illuminating unit 200 will bedescribed by referring to FIG. 5 and FIG. 6. FIG. 5 shows a structure ofthe illuminating unit 200 as viewed from the side of the object OBJ. Thediffusing section 211 is structured to be the square cylindrical shaped.Moreover, the light source section 210 is disposed on four sides roundthe square cylindrical shape. The light source section 210 is formed bythree sets of LEDs with each set including eight LEDs 210 a, 210 b, 210c, 210 d, 210 e, 210 f, 210 g, and 210 h. In other words, the lightsource section 210 is made of total of 24 (=3 sets×8) LEDs. Each of theLEDs 210 a to 210 h allows the illuminating light to emerge toward thefour sides around the diffusing section 221 having the squarecylindrical shape.

FIG. 8 shows a light emission spectrum of the eight LEDs 210 a, 210 b,210 c, 210 d, 210 e, 210 f, 210 g, and 210 h. In FIG. 8, a horizontalaxis indicates a wavelength (unit: nm) and a vertical axis indicates alight intensity (unit: arbitrary unit). The LED 210 a has a spectraldistribution with a central emission wavelength near 450 nm as shown ina curve Sa. The LED 210 b has a spectral distribution with acentral-emission wavelength near 505 nm as shown in a curve Sb. The LED210 c has a spectral distribution with a central emission wavelengthnear 525 nm as shown in a curve Sc. The LED 210 d has a spectraldistribution with a central emission wavelength near 560 nm as shown ina curve Sd. The LED 210 e has a spectral distribution with a centralemission wavelength 575 nm as shown in a curve Se. The LED 210 f has aspectral distribution with a central emission wavelength 609 nm as shownin a curve Sf. The LED 210 g has a spectral distribution with a centralemission wavelength 635 nm as shown in a curve Sg. The LED 210 h has aspectral distribution with a central emission wavelength 670 nm as shownin a curve Sh. A curve Si will be used in a third embodiment which willbe described later.

The description will be continued upon coming back to FIG. 5. As it hasbeen described above, the LED controller 115 controls an emission stateof the LEDs 210 a to 210 h. For example, the LED controller 115 puts ONthe LED 210 a which has the spectral distribution shown in the curve Sa,and puts OFF the other LEDs 210 b to 210 h. Further, the CCD 113captures an image of image data by illuminating light of the spectraldistribution shown in the curve Sa.

Next, the LED controller 115 puts OFF the LED 210 a and puts on the LED210 b having the spectral distribution shown in the curve Sb. The CCD113 captures an image of image data by illuminating light of thespectral distribution shown in the curve Sb. Further, the procedure ofputting ON and putting OFF the light is performed repeatedly for all theLEDs 210 a to 210 b. The LEDs are suitable for speedy lighting up andlighting out control.

Light from the LEDs 210 a to 210 h is advanced toward the four sidesaround circumference of the square cylinder shaped diffusing section211. Further, the light from the LEDs 210 a to 210 h receives adiffusion effect at an inner surface of the diffusing section 211. Thelight which is diffused is emerged either from the first aperturesection 212 a or from the second aperture section 212 b. The firstaperture section 212 a and the second aperture section 212 b form anaperture section. Each of the first aperture section 212 a and thesecond aperture section 212 b has an emerging section having arectangular shape.

FIG. 6 shows a cross-sectional structure of the illuminating unit 200.The diffusing section 221 has a hollow cylindrical shape of a squarepole. A detailed structure of the diffusing section 211 will bedescribed later.

Here, axes La and Lb parallel to the axis AX of the imaging opticalsystem 121 are taken into consideration. A light beam La emerged fromthe first aperture section 212 a is advanced from left to right in FIG.6. The light beam La makes and angle θa with the axis AXa, andilluminates the object OBJ. Similarly, a light beam Lb emerged from thesecond aperture section 212 b is advanced from right to left in FIG. 6.The light beam Lb makes an angle θb with an axis AXb, and illuminatesthe object OBJ.

As it has been described above, the first aperture section 212 a and thesecond aperture section 212 b are provided facing mutually with respectto the axis AX of the imaging optical system 121. Therefore, it ispossible to illuminate the object OBJ at the predetermined angles θa andθb from two mutually facing directions with the axis AX of the imagingoptical system 121 as the center. Accordingly, the object OBJ isilluminated upon being superimposed by the light from the first aperturesection 212 a and the light from the second aperture section 212 b. Theangles θa and θb are let to be 45′ or more than 45° for example.

Accordingly, incidence of specularly reflected light from the irradiatedsurface of the object OBJ on the imaging optical system 121 can bereduced. As a result of this, the imaging optical system 121 can fetchwith high efficiency only the scattered light from the irradiatedsurface of the object OBJ. Consequently, it is possible to acquire theimaging apparatus in which the specularly reflected light is reduced,and which can measure with high accuracy the color distribution of thesurface of the object OBJ. Furthermore, the illuminating unit 200illuminates the object OBJ from two different directions. Therefore, noshade is developed even for a three-dimensional object such as a tooth.

Moreover, the illuminating unit 200 is provided in an optical pathbetween the imaging optical system 121 and the irradiated surface of theobject OBJ. Further, it is more desirable to dispose the illuminatingunit 200 near a side of incidence of the imaging optical system 121.Therefore, it is possible to illuminate from two directions using oneilluminating unit 200. Furthermore, the imaging optical system 121captures an image of the scattered light which has passed through theilluminating unit 200. Therefore, it is possible to simplify a structurearound the imaging optical system. Consequently, it is possible toacquire a small sized imaging apparatus 100.

Moreover, a roof portion 213 a is formed at an outer circumferentialside of the first aperture section 212 a. Furthermore, a roof portion213 b is formed at an outer circumferential side of the second aperturesection 212 b. The roof portions 213 a and 213 b are formed to have anangle of inclination and a size such that the diffused light emergedfrom the first aperture section 212 a and the second aperture section212 b is guided efficiently toward the object OBJ.

FIG. 7A and FIG. 7B are diagrams showing a relation between a size ofthe first aperture section 212 a and an emerged light. Since the secondaperture section 212 b has the same structure as the first aperturesection 212 a, the description will be made with the first aperturesection 212 a as a representative example. As it has been describedabove, the diffusing plate 211 has the hollow cylindrical shape of asquare pole. As shown in FIG. 7A, a cross-sectional shape of thediffusing section 211 along an x-y plane is a rectangular shape. Alength of the rectangular shape in a direction along x axis is let to beL and an aperture diameter (length) of the first aperture section 212 ais let to be D1. FIG. 7B shows a structure of the first aperture section212 a having an aperture diameter D2 which is greater compared theaperture diameter D1.

In FIG. 7A, when D1/L is sufficiently small, the first aperture section212 a functions as a point light source. Therefore, light Ls emergedfrom the first aperture section 212 a becomes a substantially sphericalwave. Whereas, as shown in FIG. 7B, when D2/L is a predetermined value,light Lc emerged from the first aperture section 212 a becomes asubstantially parallel light.

In the first embodiment, when the length of the diffusing section 211along a predetermined plane (x-z plane in FIG. 6) is let to be L, and alength of the second aperture section 212 b along a predetermined plane(x-z plane) is let to be D, the apertures is formed to have a ratio D/Lso as to allow to emerge the substantially parallel light.

FIG. 9 shows both a structure of the illuminating unit 200 and a lightintensity distribution IL of the illuminated light on the optical axisAX. An intensity distribution on the optical axis AX of the light fromthe first aperture section 212 a and the second aperture section 212 bis roughly zero near the aperture section. As going away from theaperture section, the light intensity distribution IL is increased andbecomes the maximum value Im at a position Zm. Next, as going fartheraway from the position Zm, the light intensity distribution is graduallyattenuated. Here, there is almost no change in the light intensitydistribution in a direction along the optical axis AX in a range ZL, andis a substantially constant value. For example, even when an imagingdistance between the imaging apparatus 100 and the object OBJ is changedin the range ZL, the light intensity distribution of the illuminatedlight is substantially constant. In other words, even when the imagingdistance in the range ZL in a direction of focal depth, the imagingapparatus 100 can perform a satisfactory measurement with constantintensity distribution of the illuminated light.

Moreover, the first aperture section 212 a and the second aperturesection 212 b are provided to be separated only by a predeterminedinterval K. By changing the interval K between the two aperturesections, it is possible to change the position Zm of the maximum valueIm. For example, when the interval K is let to be small, the position Zmcomes closer to the illuminating unit 200. Whereas, when the interval Kis let to be large, the position Zm is moved in a direction going awayfrom the illuminating unit 200. Furthermore, when the position Zm ismoved away from the illuminating unit 200, an amount of the illuminatinglight is attenuated. Therefore, it is necessary to increase an output ofthe LEDs. Moreover, when the position Zm is too close to theilluminating unit 200, in a case of a three-dimensional object,sometimes the illuminating unit 200 and the object OBJ interfere. Togive a concrete example, when a tooth is measured as an object OBJ, inthe imaging apparatus having a small interval K between the two aperturesections, a nose of a human being and the imaging apparatus 100 make acontact. Thus, it is desirable to set the interval K to be anappropriate value according to the amount of light and a type of theobject OBJ.

As it has been described in FIG. 7A, when the substantially sphericalwave is emerged from the first aperture section 212 a and the secondaperture section 212 b, if the position on the optical axis AX differs,a change in the light intensity distribution becomes large. Whereas, asshown in FIG. 7B, when the substantially parallel light is emerged fromthe first aperture section 212 a and the second aperture section 212 b,the change in the light intensity distribution according to the positionalong the optical axis AX is reduced as compared to the change in thelight intensity distribution in FIG. 7A Thus, in the first embodiment,the first aperture section 212 a and the second aperture section 212 bhave the aperture diameter D2 of a size such that the illuminated lightwhich is scattered at the diffusing section 211 is emerged as thesubstantially parallel light (refer to FIG. 7B). Accordingly, the lightintensity distribution in the x-y plane in a direction substantiallyperpendicular to the optical axis AX is uniform, and the change in theamount of light in a z direction along the optical axis AX is reduced.Therefore, it is possible to measure with high accuracy the colordistribution of the surface of the object OBJ. Light emerged through thefirst aperture section 212 a and the second aperture section 212 b isnot restricted to the substantially parallel light, and may be gentle(having a large radius of curvature) convergent light or gentledivergent light.

(Structure of Diffusing Section)

FIG. 10A shows a cross-sectional structure of the diffusing section 211.The diffusing section 211 includes a resin portion 1000. A thickness ofthe resin portion 1000 is about 1 mm to 2 mm for example. On a surfaceof the resin portion 1000, on a side opposite to the light sourcesection 210, an aluminum layer 1001 is formed by metal deposition. Theresin portion 1000 diffuses light from the light source section 210.Moreover, the aluminum layer 1001 reflects light which is passed throughthe thin resin portion 1000. The reflected light is scattered by beingincident again on the resin portion 1000. Accordingly, it is possible toreduce the amount of light which is lost by transmission through theresin portion 1000.

As it has been mentioned above, the light source section 210 is formedby the LEDs 210 a to 210 h, each supplying light of different wavelengthrange. Further, a position at which each of the LEDs 210 a to 210 h isinstalled is different. Therefore, for example, for light emitted fromthe LED 210 a and light emitted from the LED 210 h, opticalcharacteristics such as an illuminance distribution differ. The resinportion 1000 scatters light from each of the LEDs 210 a to 210 h.Accordingly, it is possible to reduce a variation in the opticalcharacteristics caused due to a difference in disposing the LEDs 210 ato 210 h.

Moreover, the roof portion 213 is formed near the first aperture section212 a. The roof portion 213 a, as it has been described above, has theangle of inclination and the size such that the scattered light isguided efficiently toward the object OBJ. For example, when the roofportion 213 a is not provided, light not advancing toward the object OBJis generated. Therefore, the amount of light is lost. Moreover, when theroof portion 213 a is provided perpendicularly (parallel to the opticalaxis AX), the light which is specularly reflected at the roof portion213 a is incident on the object OBJ. Thus, the roof portion 213 a alsoserves a function of returning the light specularly reflected at theroof section 213 a, out of the light from the light source section 210,toward an inside of the diffusing section 211. Therefore, it is possibleto reduce incidence of the specularly reflected light from the roofportion 213 a, on the object OBJ.

FIG. 10B shows a cross-sectional structure of a modified example of thediffusing plate 211. A reflecting coat layer 1101 is formed on an innersurface of the diffusing section 211. A diffusing coat layer 1100 isfurther formed on the reflecting coat layer 1101. The diffusing coatlayer 1100 can be formed by applying barium sulfate for example.Accordingly, the diffusing coat layer 100 diffuses the light which isincident. Thus, a film of a high reflectance (coat layer) and a film ofa high diffusivity (coat layer) may be stacked in two layers, or may beformed by using other material. Moreover, in the first embodiment, thelight source sections 210 are disposed at four sides of the illuminatingunit 200. However, it is not required to necessarily dispose the lightsource sections 210 at all four sides. The structure may such that in anacceptable range in which there does not arise a problem of an effect ofa change of color and color distribution including a change in abrightness and light distributing characteristics of a light source, thelight source sections 210 are disposed on two sides facing one anotherin a horizontal direction or in a vertical direction and the lightsource sections 210 are not disposed on the remaining two side, or thelight source sections 210 are disposed on three sides and the lightsource section 210 is not disposed on one side. In this case, effectssuch as a decrease in the number of LEDs used and a reduction in thesize of the light source section can be desired.

FIG. 10C shows another modified example of the diffusing section 211.For example, a diffusing coat layer 1150 is formed on an aluminumsubstrate 1151 which is a reflecting surface. Accordingly, it ispossible to manufacture the diffusing section 211 easily by using thealuminum substrate 1151.

In any of the structures in FIG. 10A to FIG. 10C, it is possible to makeuniform the intensity distribution of the illuminated light by improvingthe diffusion characteristics of the diffusing section 211. Moreover, byimproving the diffusion characteristics, it is possible to improve anefficiency of light. Furthermore, each of the LED 210 a to 210 h isdisposed to emit the light toward the outer circumference of thediffusing section 211. Accordingly, it is possible to reduce directemergence of light supplied from each of the LEDs 210 a to 210 h, fromthe first aperture section 212 a and the second aperture section 212 b.According to this arrangement, it is possible to improve a lightdiffusing efficiency of the diffusing section 211.

A lens may be disposed near the first aperture section 212 a and thesecond aperture section 212 b. The lens has a function of guiding towardthe object OBJ, upon allowing to refract the light diffused at thediffusing section 211. Accordingly, it is possible to illuminate theobject efficiently by the light which is diffused.

SECOND EMBODIMENT

A structure of an illuminating unit 1200 according to a secondembodiment will be described by referring to FIG. 11 and FIG. 12. Samereference numerals are assigned to components same as in the firstembodiment, and the description to be repeated is omitted. FIG. 11 showsa structure of the illuminating unit 1200 as seen from the side of theobject OBJ. Moreover, FIG. 12 shows a cross-sectional structure of theilluminating unit 1200. As shown in FIG. 11, the diffusing section 211is formed to have an annular cylindrical shape. The light source section210 is disposed on an inner circumferential side of the annularcylindrical shape. The light source section 210 includes the LEDs 210 a,210 b, 210 c, 210 d, 210 e, 210 f, 210 g, and 210 h. In FIG. 11, twoLEDs each of the LED 210 a, 210 b, and 210 c are shown. Thus, theilluminating unit 1200 has total of 12 LEDs disposed at substantiallyequal interval. Each of the LEDs 210 a to 210 h is structured to emitlight toward the outer circumference of the diffusing section 211.

As shown in FIG. 12, a cross section of a diffusing section 1211 iscircular shaped. Due to this shape, it is possible to improve theefficiency of the illuminating light. Moreover, similarly as in thefirst embodiment mentioned above, when the length of the diffusingsection 1211 along the predetermined plane (x-z plane in FIG. 12) is letto be L, and a length of the first aperture section 212 a and the secondaperture section 212 b along a predetermined plane is let to be D, theaperture is formed to have a ratio D/L so as to allow to emerge thesubstantially parallel light.

Moreover, the first aperture section 212 a and the second aperturesection 212 b are provided to be separated only by a predetermineddistance K such that the position Zm (refer to FIG. 9) of the maximumvalue Im is optimum.

In the second embodiment, 12 LEDs 802 a to 802 h are repeatedly put ONand OFF one after the other. Further, the object OBJ is illuminated bythe illuminated light from the LED which is put ON. Moreover, a positionat which each of the LEDs 802 a to 802 h is disposed in a circular shapeis different. The diffusing plate 1211 generates diffused light having asubstantially uniform intensity distribution, irrespective of the lightdistribution characteristics of each of the LEDs 802 a to 802 h.Therefore, it is possible to reduce a variation in the opticalcharacteristics caused due to a difference in the positions of the LEDs.Moreover, the diffusing section 1211 is not restricted to be annularcylindrical shaped as shown in FIG. 11. For example, the diffusingsection 1211 may let to be elliptical annular cylindrical shaped havinga major axis and a minor axis, when viewed from the side of the objectOBJ. At this time, it is desirable that the first aperture section 212 aand the second aperture section 212 b are provided in a direction alongthe major axis. Accordingly, it is possible to reduce the size whileimproving the diffusion efficiency.

THIRD EMBODIMENT

A structure of an illuminating unit 1300 according to a third embodimentwill be described below by referring to FIG. 13. Same reference numeralsare assigned to components same as in the first and the secondembodiment, and the description to be repeated is omitted. FIG. 13 showsa structure of the illuminating unit 1300 as viewed from the side of theobject OBJ.

The diffusing section 211 is formed to have a continuous cylindricalshape encircling the optical axis AX which is a predetermined axis.Moreover, by the cylindrical shaped diffusing section 211, a space of apredetermined shape is formed near the optical axis AX which is thepredetermined axis. Light from the illuminating unit 1300 is reflectedat the surface of the object OBJ, and scattered. The scattered light ispassed through the space having the predetermined shape, of theilluminating unit 1300, and is incident on the imaging optical system121. Thus, it is possible to dispose the illuminating unit 1300 near anend surface of incidence of the imaging optical system 121. As a result,it is possible to reduce a size of the entire imaging apparatus.

Moreover, the space having the predetermined shape is formed to besubstantially square shaped by four surfaces (sides) 1310 a, 1310 b,1310 c, and 1310 d on an inner circumference of the diffusing section211. An imaging surface of the CCD 113 has a square shape. Therefore,when the size of the imaging apparatus is reduced, it is possible toreduce a vignetting of light due to a peripheral portion of the squareshaped space of the illuminating unit 1300.

Moreover, the light source section 210 is formed by four sets of LEDs,each set including three LEDS 210X, 210Y, and 210Z. In other words, thelight source section 210 is made of total of 12 (=4 sets×3) LEDs. Eachof the LEDs 210X, 210Y, and 210Z is provided on the two surfaces 1310 band 1310 d of the diffusing section 211 on a side of the optical axisAX. Similarly as in the first embodiment and the second embodiment, thefirst aperture section 212 a and the second aperture section 212 b areprovided at the positions facing each other with respect to the opticalaxis AX. Further, the light source section 210 is provided on thesurface of the diffusing section 211 on the side of the optical axis AXor near the surface of the diffusing section 211 on the side of theoptical axis AX. Concretely, each of the LEDs 210X, 210Y, and 210Z isprovided on the surfaces 1310 b and 1310 d on the inner side of thediffusing section 211. Moreover, each of the LEDs 210X, 210Y, and 210Zemits illuminating light from the inner circumference of the cylindershaped diffusing section 211 toward four sides on the outercircumference. As a result, it is possible to structure the diffusingsection 211 compactly. Moreover, it is possible to make a width W of thediffusing section small. Accordingly, it is possible to reduce the sizeof the illuminating unit 1300 and to save the space. Furthermore, bydisposing the light source section 210 on the inner side, it is possibleto improve the diffusion efficiency of light in the diffusing section211. Consequently, it is possible to illuminate the object OBJ by brightilluminating light. As compared to the annular cylinder shaped diffusingsection in the second embodiment, by structuring the diffusing sectionto have a square cylindrical shape as in the third embodiment, it ispossible to further increase the diffusion efficiency.

Moreover, the LEDs 210X, 210Y, and 210Z are provided at positions suchthat the illuminating light supplied from the LEDs 210X, 210Y, and 210Zis emerged from the aperture sections 212 a and 212 b upon reflecting atleast once at the diffusing section 211. In other words, when theaperture sections 212 a and 212 b are observed from the side of theobject OBJ, the LEDs 210X, 210Y, and 210Z are disposed at positions atwhich, direct light from the LEDs 210X, 210Y, and 210Z, in other wordslight which is not reflected even once at the diffusing section 211,cannot be observed. It is desirable that the aperture sections 212 a and212 b allow the diffused light to be emerged efficiently. In the thirdembodiment, the light supplied from the LEDs 210X, 210Y, and 210Z isemerged from the aperture sections 212 a and 212 b upon being reflectedonce without fail at the diffusing section 211. Therefore, from amongthe light emitted from the LEDs 210X, 210Y, and 210Z, it is possible toreduce light which is emerged directly from the aperture sections 212 aand 212 b without being reflected at the diffusing section 211. As aresult of this, the illuminating unit 1300 can illuminate the object OBJby satisfactory diffused light.

Next, a structure of each of the LEDs 210X, 210Y, 210Z will bedescribed. FIG. 14A, FIG. 14B, and FIG. 14C show a structure of each ofthe LEDs 210X, 210Y, and 210Z as viewed from a front side. As shown inFIG. 14A, the LED 210X has three light emitting sections 214 a, 214 b,and 214 c. Moreover, as shown in FIG. 14B, the LED 210Y has three lightemitting sections 214 d, 214 e, and 214 f. Furthermore, as shown in FIG.14C, the LED 210Z has three light emitting sections 214 g, 214 h, and214 i.

A spectral distribution of the illuminating light which is supplied fromeach of the emitting sections will be described by referring to FIG. 8.The light emitting section 214 a has a spectral distribution with acentral emission wavelength near 450 nm as shown in the curve Sa. Thelight emitting section 214 b has a spectral distribution with a centralemission wavelength near 505 as shown in the curve Sb. The lightemitting section 214 c has a spectral-distribution with a centralemission wavelength near 525 nm as shown in curve Sc. Thus, the LED 210Xcan supply light of three different wavelength ranges from one package.

Moreover, the light emitting section 214 d has a spectral distributionwith a central emission wavelength near 560 nm as shown in the curve Sd.The light emitting section 214 e has a spectral distribution with acentral emission wavelength near 575 nm as shown in the curve Se. Thelight emitting section 214 f has a spectral distribution with a centralemission wavelength 609 nm as shown in the curve Sf. Thus, the LED 210Ycan supply light of three different wavelength ranges from one package.

Furthermore, the light emitting section 214 g has a spectraldistribution with a central emission wavelength 635 nm as shown in thecurve Sg. The LED 214 h (light emitting section 214 h) has a spectraldistribution with a central emission wavelength 670 nm as shown in thecurve Sh. The LED 214 i (light emitting section 2141) has a spectraldistribution with a central emission wavelength 700 nm as shown in thecurve Si. Thus, the LED 210Z can supply light of three differentwavelength ranges from one package.

Accordingly, from the three LEDs 210X, 210Y, and 210Z, the light of ninedifferent wavelength ranges, in other words nine bands, can be supplied.As a result of this, it is possible to reduce a variation in a lightemitting position of light for each different wavelength range.Consequently, it is possible to reduce a change in illuminationunevenness according to illuminating light of different colors. Theemission wavelength range of each of the nine light emitting sections214 a to 214 i may not be let to be different. For example, from amongthe nine light emitting sections 214 a to 214 i, the light emissionwavelength of the two light emitting sections may be let to besubstantially same. At this time, light of eight different wavelengthranges, in other words light of eight bands can be supplied by the ninelight emitting sections 214 a to 214 i.

Similarly, it is possible to control the number of bands of the lightsupplied by the LEDs 210X, 210Y, and 210Z to appropriate desirablenumber. For example, it is possible to structure each of the LEDs 210X,210Y, and 210Z to have three light emitting sections, each supplying Rlight (red color), G light (green color), and B light (blue color).According to this structure, it is possible to acquire a three-bandcolor camera of R light, G light, and B light.

Moreover, it is possible to use an LED which supplies white color light,as the light source section. In this case, a color CCD which includes anR light transmission filter, a G light transmission filter, and a Blight transmission filter is used as the CCD 113. Moreover, the objectOBJ is illuminated by the white color light. Light scattered from theobject OBJ is imaged at the color CCD. When three types of color filtersare used, it is equivalent to a three-band illumination. Consequently,when the number of color filters of different transmission wavelengthrange is increased, it is possible to have multiple bands according tothe number of color filters.

The shape of the diffusing section, the mode of disposing the LEDs, andthe size and the position of the aperture section are not restricted tothe embodiments described above. For example, when the diffusing sectionwithout being restricted to the continuous cylindrical structure, has aspace for diffusing, any structure may be used.

Furthermore, the LED having a plurality of light emitting sections inone package as shown in the third embodiment may be used in theilluminating unit of the first embodiment or the second embodiment.Thus, the present invention is not restricted to each of the embodimentsmentioned above, and various modifications in a scope which fall withinthe basic teaching of the present invention are possible

INDUSTRIAL APPLICABILITY

Thus, it is possible to use appropriately an illuminating unit accordingto the present invention at the time of illuminating in an imagingapparatus which measures a color distribution of a surface of an object.

1-11. (canceled)
 12. An illuminating unit which is used in an imagingapparatus which includes an imaging optical system, comprising: a lightsource section which supplies an illuminating light; a diffusing sectionwhich diffuses by reflecting the illuminating light from the lightsource section; and an aperture section which allows a diffusedilluminating light to emerge, wherein the aperture section has adiameter which allows the diffused illuminating light to emerge as asubstantially parallel light, and an angle between an optical axis ofthe imaging optical system and the substantially parallel light is 45°or greater than 45°.
 13. An illuminating unit which is used in animaging apparatus which includes an imaging optical system, comprising:a light source section which supplies an illuminating light; a diffusingsection which diffuses by reflecting the illuminating light from thelight source section; and an aperture section which allows a diffusedilluminating light to emerge, wherein the light source section has aplurality of light emitting sections which supply light of differentwavelength range respectively, and the aperture section has a diameterwhich allows the diffused illuminating light to emerge as asubstantially parallel light, and an angle between an optical axis ofthe imaging optical system and the substantial parallel light is 45° orgreater than 45°.
 14. An illuminating unit which is used in an imagingapparatus which includes an imaging optical system, comprising: a lightsource section which supplies an illuminating light; a diffusing sectionwhich diffuses by reflecting the illuminating light from the lightsource section; a diffusing section which diffuses by reflecting theilluminating light from the light source section; and an aperturesection which allows a diffused illuminating light to emerge, whereinthe light source section is provided at a position at which theilluminating light supplied by the light source section is emerged fromthe aperture section, upon being reflected at least once in thediffusing section, and an angle between an optical axis of the imagingoptical system and the substantially parallel light is 45° or greaterthan 45°.
 15. An illuminating unit which is used in an imaging apparatuswhich includes an imaging optical system, comprising: a light sourcesection which supplies an illuminating light; a diffusing section whichdiffuses by reflecting the illuminating light from the light sourcesection; and an aperture section which allows a diffused illuminatinglight to emerge, wherein the light source section has a plurality oflight emitting sections, each supplying light of different wavelengthrange, and the light source section is provided at a position at whichthe illuminating light supplied by the light source section is emergedfrom the aperture section upon being reflected at least once in thediffusing section, and an angle between an optical axis of the imagingoptical system and the substantially parallel light is 45° or greaterthan 45°.
 16. The illuminating unit according to any one of claims 12 to15, wherein: the aperture section includes a first aperture section anda second aperture section which are provided at a predeterminedinterval.
 17. The illuminating unit according to claim 16, wherein: thefirst aperture section and the second aperture section are provided atpositions facing with respect to a predetermined axis.
 18. Theilluminating unit according to claim 17, wherein: the light sourcesection is provided on a surface of the diffusing plate, on a side ofthe predetermined axis, or near the surface of the diffusion plate, onthe side of the predetermined axis.
 19. The illuminating unit accordingto claim 17, wherein: the diffusing section is formed to be continuouscylindrical shaped, encircling the predetermined axis, and a space of apredetermined shape is formed near the predetermined axis, by thecylindrical shaped diffusing section.
 20. The illuminating unitaccording to claim 19, wherein: the space of the predetermined shape isa substantially square shaped.
 21. The illuminating unit according toclaims 12 or 13, wherein: the light source section is provided at aposition at which the illuminating light supplied by the light sourcesection is emerged from the aperture section upon being reflected atleast once in the diffusing section.
 22. An imaging apparatuscomprising: the illuminating unit according to any one of claims 12 to15; and the imaging optical system which forms an image of a reflectedlight from an irradiated surface which is illuminated by theilluminating unit, and wherein: a color distribution of the irradiatedsurface is calculated based on the reflected light acquired by theimaging optical system.